Quantification and molecular imaging of fatty acid isomers from complex biological samples by mass spectrometry

Elucidating the isomeric structure of free fatty acids (FAs) in biological samples is essential to comprehend their biological functions in various physiological and pathological processes. Herein, we report a novel approach of using peracetic acid (PAA) induced epoxidation coupled with mass spectrometry (MS) for localization of the C=C bond in unsaturated FAs, which enables both quantification and spatial visualization of FA isomers from biological samples. Abundant diagnostic fragment ions indicative of the C=C positions were produced upon fragmentation of the FA epoxides derived from either in-solution or on-tissue PAA epoxidation of free FAs. The performance of the proposed approach was evaluated by analysis of FAs in human cell lines as well as mapping the FA isomers from cancer tissue samples with MALDI-TOF/TOF-MS. Merits of the newly developed method include high sensitivity, simplicity, high reaction efficiency, and capability of spatial characterization of FA isomers in tissue samples.

Automated summary

This study presents a novel method using PAA-induced epoxidation combined with mass spectrometry to localize the C=C bond in unsaturated fatty acids, allowing for quantification and spatial visualization of FA isomers in biological samples.